alias: ensure checksignature() is applied directly to the command (issue2286)

Aliased commands that received bad arguments would raise TypeError instead of
SignatureError. This only affected commands that weren't wrapped by extensions.
Using util.checksignature() in cmdalias.__call__() ensures SignatureError is
raised correctly.

mercurial/dispatch.py

@@ -248,7 +248,7 b' class cmdalias(object):'
         if self.shadows:
             ui.debug("alias '%s' shadows command\n" % self.name)
 
-        return self.fn(ui, *args, **opts)
+        return util.checksignature(self.fn)(ui, *args, **opts)
 
 def addaliases(ui, cmdtable):
     # aliases are processed after extensions have been loaded, so they

tests/test-alias

@@ -14,6 +14,7 b" shortlog = log --template '{rev} {node|s"
 dln = lognull --debug
 nousage = rollback
 put = export -r 0 -o "\$FOO/%R.diff"
+rt = root
 
 [defaults]
 mylog = -q
@@ -64,3 +65,8 b' hg dln'
 echo '% path expanding'
 FOO=`pwd` hg put
 cat 0.diff
+
+echo '% invalid arguments'
+hg rt foo
+
+exit 0

tests/test-alias.out

@@ -43,3 +43,16 b' diff -r 000000000000 -r e63c23eaa88a foo'
 +++ b/foo	Thu Jan 01 00:00:00 1970 +0000
 @@ -0,0 +1,1 @@
 +foo
+% invalid arguments
+hg rt: invalid arguments
+hg rt 
+
+alias for: hg root
+
+print the root (top) of the current working directory
+
+    Print the root directory of the current repository.
+
+    Returns 0 on success.
+
+use "hg -v help rt" to show global options